The claimed invention relates to the field of articles molded to final shape from materials such as wood and paper pulp, plastics such as thermoplastics, and the like, for the packaging, shipping and retail merchandizing of fragile articles such as eggs, and more particularly to the style of molded egg carton having a pocketed bottom section and a pair of opposed inwardly foldable trough-shaped cover sections.
Prior to the present invention, it was known for many years to provide egg cartons made of cardboard or similar sheet material which had a pair of opposed inwardly foldable flat cover sections latchable by tuck-in tabs or other means to the pocketed bottom section in the closed position. Buttery U.S. Pat. No. 2,382,202 issued Aug. 14, 1945 discloses a collapsible carton of this nature, but a principal drawback to such cardboard cartons is the requirement that they must be "set up" -- including a folding operation and a tab insertion, gluing or similar operation -- after receipt from the carton manufacturer and before they are ready for packaging eggs.
The development of molded egg cartons eliminated the necessity of setting up the cartons at the point of egg packaging. Originally molded of paper and wood pulp materials, and now molded from thermoplastic materials as well as pulp, molded cartons can be nested one within the other in the empty condition in compact, rugged stacks for safe and inexpensive bulk shipment from the carton manufacturer to the egg packager. When unstacked, filled with eggs, and the covers closed by the egg packager, molded cartons provide an attractive, sturdy and inexpensive package for the shipment and retail merchandizing of eggs. Many different styles and arrangements of closable covers and locking mechanisms have been proposed for and used on molded egg cartons, some of which have proved to be commercially successful and some of which have not.
The present invention relates to the type of molded cartons -- as opposed to cartons cut from flat sheet stock -- wherein the closable cover takes the form of a pair of mirror image cover sections which are originally molded in an outward open position hingedly connected to the pocketed bottom section for folding thereover to a closed position. Numerous variations of this type of cover for molded egg carton have been proposed, and a continuing problem has been to insure that the cover sections are securely latchable in the closed position while at the same time providing a substantially uninterrupted flat upper cover surface to display advertising information and/or content information.
A survey of representative prior disclosures confirms that skilled designers of molded carton and other products have worked for many years to fill the long felt want for a carton which would meet these objectives. For instance, Chaplin U.S. Pat. No. 2,423,756 issued July 8, 1947 discloses tabs for holding one cover section against the other in the closed position (not locking the cover sections to the bottom section). Schwertfeger U.S. Pat. No. 2,591,471 issued Apr. 1, 1952 discloses detents (not projections) for latching the cover sections to the bottom section in the closed position. Vahle U.S. Pat. No. 2,933,227 issued Apr. 19, 1960 discloses cover sections molded so that the base or top walls join the walls which become the central walls in the closed position at an angle of about 90.degree. (without positive latching means). Comstock U.S. Pat. No. 3,191,844 issued June 29, 1965 discloses a manner of molding trough-shaped cover sections so that in the closed position their base or top walls form a plane smooth top free from indentations for various printing designs (without positive latching means). Trimble U.S. Pat. No. 3,307,765 issued Mar. 7, 1967 discloses troughshaped cover sections molded so that the base or top walls join the central or mid-walls at an angle of about 90.degree. (without positive latching means). Newman U.S. Pat. No. 3,568,915 issued Mar. 9, 1971 discloses a male element which protrudes outwardly from the mid-wall of one trough-shaped cover section and an aperture through the mid-wall of the other trough-shaped cover section to latch them together in the closed position (not locking the cover sections to the bottom section). French U.S. Pat. No. 3,580,480 issued May 25, 1971 discloses projections on the mid-wall of each cover section directed away from the centerline of the carton for latching the cover sections to the bottom section in the closed position.
The molded cartons disclosed in the aforesaid patents all seek to provide a substantially uninterrupted flat upper cover surface, which requires that the mid-walls of the cover sections are vertically against each other in the closed condition without a longitudinal crevice along the center of the carton top. This requirement militates against the use of locking mechanisms on the mid-walls which project toward each other when the cover sections are in the closed position. For this reason it has heretofore been the dogma of the art that hook or beak type male locking projections -- such as those for use with nonanalogous types of covers disclosed for example in Friday U.S. Pat. No. 2,873,057 issued Feb. 10, 1959, and Hartmann U.S. Pat. No. 3,276,656 issued Oct. 4, 1966 -- would not be applicable to the mid-lock style of cover arrangement for molded egg cartons.
By the same token, the concept of exterior windows for viewing the contents of the egg pockets is previously known, for instance, from Reifers U.S. Pat. No. 3,388,852 issued June 18, 1968, and Crabtree U.S. Pat. No. 3,647,132 issued Mar. 7, 1972. Such windows have not heretofore been utilized, however, for the supplemental purpose of controlling the inherent resilience characteristics of the cover section hinges to cooperate with positive locking mechanism in a manner which insures that the cover sections in the closed position provide a substantially uninterrupted flat upper cover surface.
Thus, the problem which has been long recognized as documented above, but heretofore unsolved is the provision of a molded egg carton having opposed cover sections which fold together and are positively latched to the bottom section in the closed position, yet are easily unlatchable, in a simplified manner which provides a substantially uninterrupted flat upper cover surface.